The present application is based on Japanese Patent Application No. 2001-125136, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a semiconductor light-emitting device.
2. Description of the Related Art
Recently, in order to excite a photocatalyst in an air purifier of an automobile, a light-emitting device (LED) emitting ultraviolet light is utilized. This LED has a configuration in which numbers of group III nitride compound semiconductor light-emitting elements are mounted on an exclusive design substrate and sealed with a light-transmissive resin such as a silicone resin.
In the case where such an air purifier is developed for house use, the volume of air treatment increases largely. Accordingly, the light quantity of ultraviolet rays required for the photocatalyst also increases. As a result, a high light output is required of each LED. It can be considered that the required high light output of the LEDs may be carried out by increasing the number of LEDs. This consideration is not preferable because the increase of the number of parts causes an increase in cost.
According to the investigation conducted by the present inventors, it has been found that following problems arise when the light output of the related-art LED is made large.
With the increase of the light quantity, discoloration (yellowing) of a sealing resin generally used is accelerated so that a sufficient lifetime of the related-art LED cannot be ensured.
There is a possibility that an air purifier for house use is used at a high humidity compared with that for vehicle house. The air purifier for house use is therefore impossible to obtain sufficient damp-proof effects when a silicone resin effective in resistance to discoloration is used.
Further, in order to expand the market of LED into general household articles, it is not preferable to use an exclusive design substrate, but it is preferable to use a substrate in same assembling method as a general round type lamp. Further, in order to prevent the light-emitting element from being degraded due to static electricity in the assembling step, it is necessary to surely cut off the reverse current so as not to flow into the light-emitting element.
It is an object of this invention to solve at least one of these problems.
It is another object of this invention to provide a light-emitting device which has high reliability in operation and which can achieve a long lifetime.
The configuration of the light-emitting device according to this invention is as follows: a semiconductor light-emitting device having: a group III nitride compound semiconductor light-emitting element subjected to flip chip bonding for emitting light with a wavelength not longer than 400 nm; a Zener diode coupled to the light-emitting element; and a metal casing having a window and for sealing the light-emitting element and the Zener diode.
In the light-emitting device having such a configuration, a group III nitride compound semiconductor light-emitting element is subjected to flip chip bonding so that light can be extracted from the light-emitting element to the outside with high efficiency. By using a Zener diode, a reverse current can surely prevented from flowing into the light-emitting element. Accordingly, not only can the light-emitting device be produced in an ordinary assembling step but also the reliability and durability of the light-emitting device per se can be improved. Further, when the light-emitting element is sealed with a metal casing, any influence of the external environment (particular humidity) giving to the light-emitting element can be blocked. Accordingly, reliability and durability of the light-emitting device are improved. On the other hand, the use of the sealing resin can be omitted due to the use of the metal casing. In such a manner, the problem of discoloration can be solved. Further, according to the invention, the light-emitting element is coated with a silicone resin high in resistance to discoloration against short-wave light radiation. By using the silicone resin higher in refractive index than air, the light is more easily emitted, thus, the light output efficiency is improved. Further, the mechanical strength of the light-emitting device is also improved.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.